The present invention is directed to a spray type coating apparatus in which paint is sprayed on a vertically moving web, and more specifically to means for effectively removing the oversprayed paint on both sides of the moving web.
Previously, an electrostatic coating system was employed in which the material to be coated was coated with paint which was atomized in an electric filed in a coating chamber. In such a system a disk-type, bell-type or gun-type electrostatic coating device was provided in the coating chamber and the materials to be coated were hung on hangers moving along a conveyor rail so that the materials were coated with paint which atomized in the electric field by the apparatus. As a further example, Japanese Patent Application No. 28740/1980 discloses an electrostatic coating method in which a moving web is coated with paint which is atomized in an electric field.
On the other hand, Japanese Laid-Open Patent Application No. 142558/1980 discloses a technique for providing a coating pattern according to an electrostatic coating method wherein, in order to improve a conventional circular or annular pattern, a shield plate to which a high voltage is applied and an air-curtain shaped air flow are utilized so that the coating pattern of the atomizer is rendered eliptical by the electrostatic force and by the force of the air flow. No matter what coating pattern is used, in order to form a coating which has a uniform thickness along both edge portions of the moving web which is being coated with paint according to the electrostatic coating method, the coating pattern must have a width larger than the width of the web. Thus, a considerable amount of overspray liquid occurs on both sides of the web.
Japanese Laid-Open Patent Application No. 104572 discloses a spraying method wherein a belt conveyor is confronted with the peripheral portion of the region to be sprayed so that the belt conveyor receives paint which is sprayed along the peripheral portion so that the peripheral portion is protected from being sprayed with paint. However, such a method is disadvantageous in that the equipment is intricate and expensive. In addition, when a moving web is being continuously coated, the overspray liquid causes the edge portion of the web to be thick coated and the paint has a tendency to flow over the rear surface of the web. Since no means are provided against the troubles which may occur when a moving web curls or flutters, the above-described difficulties relating to the thick coated edges are not sufficiently eliminated.